1. Field of the Invention
The present invention relates to combination fluid valves, and in particular to combination valves comprising an inverted bidirectional valve in combination with an umbrella valve capable of providing flow responsive to changes in pressure differential.
2. Description of the Related Art
Current combination fluid valves include those of the duckbill-umbrella variety. Duckbill-umbrella combination valves allow fluid (often air) into a container or pump chamber via the umbrella valve portion along a first flow path and allow a second fluid (often a liquid product) out of the container or pump chamber via the duckbill valve portion through a second flow path. However, the duckbill portion of the valve typically provides only limited prevention of flow in the dispensing direction and can leak under relatively low pressure differentials. For example, duckbill-umbrella combination valves can leak when used in conjunction with containers of liquid that are inverted during use.
It would be desirable to have a simple, unitary combination valve that is normally closed and allows fluid to be drawn out under differential pressure. A normally closed valve minimizes problems associated with spilling or dripping. It would also be desirable to have a combination valve that operates satisfactorily to prevent flow until a predetermined amount of pressure is achieved.